From molecules to populations energy budgets in the causality of toxic effects Tjalling Jager Dept. Theoretical Biology

Aim: ‘Quantitative bioenergetics’

Dept. Theoretical Biology Aim: ‘Quantitative bioenergetics’  Head of dept.: Prof. Bas Kooijman  Permanent staff: Dr. Bob Kooi and Dr. Tjalling Jager  PhD students in Amsterdam: Jan Baas: NoMiracle, mixture toxicity Daniel Bontje: ModelKey, food-chain toxicity Anne Willem Omta: organic carbon pump Jorn Bruggeman: organic carbon pump George van Voorn: bifurcation analysis

Causality How to link toxicant concentrations to whole- organism and population effects? toxicant effects on individual/population NOEC/ECx MoA energy budgets CBR

Precondition 1 All concepts in causality chain should explicitly consider exposure time  Toxicity is a process in time uptake into organism takes time biomarker responses can/will change in time NOEC/ECx/CBR values can/will change in time

EC10 in time Alda Álvarez et al. (2006) carbendazim time pentachlorobenzene time survival body length cumul. repro body length cumul. repro concentration

Precondition 2 Causality chain should cover all life-history aspects  Feeding, development, growth and reproduction are linked … NOEC/ECx/CBR differ between endpoints what about molecular mechanism of action?

‘Narcotic’ effects time EC10 time body size reproduction A. nanus C. elegans

Causality of effects toxicant statistics e.g., NOEC/ECx effects on individual/population

Causality of effects target sitetoxicant molecular mechanism effects on individual/population CBRs etc.

Causality of effects ENERGY BUDGET rest of the organismtarget sitetoxicant molecular mechanism physiological mechanism effects on individual/population

Energy budgets

growth reproductionassimilation Each ‘MoA’ has specific effects on life cycle (direct/indirect) Each ‘MoA’ has specific effects on life cycle (direct/indirect) maintenance

reproduction DEB theory growth maintenance assimilation Kooijman (2000) (first edition 1993)

DEB theory Kooijman (2000) (first edition 1993) Quantitative theory; ‘first principles’ time, energy and mass balance Life-cycle of the individual links levels of organisation: molecule  ecosystems Fundamental, but practical applications bioproduction, biodegradation, (eco)toxicity, sewage treatment, climate change, …

DEB allocation rules foodfaeces reserves assimilation structure somatic maintenance  1-  maturity offspring maturity maintenance

DEB model Toxicants: DEBtox energy-budget parameter toxicokinetics Life-cycle effects Kooijman & Bedaux, 1996 (Wat. Res.) Jager et al., 2006 (Ecotoxicology)

Target: maintenance time cumulative offspring time body length triphenyltin Crommentuijn et al. (1997), Jager et al. (2004)

Target: costs for growth time body length time cumulative offspring pentachlorobenzene Alda Álvarez et al. (2006)

Target: hazard to embryo time cumulative offspring time body length Chlorpyrifos Crommentuijn et al. (1997), Jager et al. (2007)

‘Non-toxicant’ effects foodfaeces reserves structure maturity offspring maturity maintenancesomatic maintenance assimilation  1-   ‘Gigantism’ parasites in snails and Daphnia  Decreased size at maturity parasites and kairomones in Daphnia Gorbushin and Levakin (1999)

Experiments nematodes Species Caenorhabditis elegans and Acrobeloides nanus Chemicals cadmium, pentachlorobenzene and carbendazim Exposure in agar Endpoints survival, body size, reproduction over full life cycle Alda Álvarez et al., 2005 (Func. Ecol.), 2006 (ES&T), 2006 (ET&C)

length eggs survival C. elegans and cadmium Mode of action: assimilation Alda Álvarez et al. (2005) time (days)

A. nanus and cadmium Mode of action: costs for growth Alda Álvarez et al. (2006)

Physiological MoA C. elegansA. nanus PeCB (narcotic) Cadmium (heavy metal) Carbendazim (inhibits mitosis)

Physiological MoA C. elegansA. nanus PeCB (narcotic) costs for growth and reproduction assimilation Cadmium (heavy metal) Carbendazim (inhibits mitosis)

Physiological MoA C. elegansA. nanus PeCB (narcotic) costs for growth and reproduction assimilation Cadmium (heavy metal) assimilationcosts for growth (+ ageing) Carbendazim (inhibits mitosis)

Physiological MoA C. elegansA. nanus PeCB (narcotic) costs for growth and reproduction assimilation Cadmium (heavy metal) assimilationcosts for growth (+ ageing) Carbendazim (inhibits mitosis) assimilation (- ageing)

Population consequences growth reproductionassimilation maintenance

Population consequences

Each ‘MoA’ has specific effects for populations assimilationreproduction growth maintenance

Extrapolate to populations Constant environment: populations grow exponentially ‘intrinsic rate of increase’ calculate from reproduction and survival in time

concentration (mg/L) concentration (mg/L) intrinsic rate (d -1 ) Extrapolate to populations 95% 90% 95% 90% Mode of action: assimilation Mode of action: costs for growth Cadmium

Conclusions Simple summary statistics are quite useless … NOEC/ECx change in time and differ between endpoints not helpful to derive CBRs on basis of ECx Molecular mechanism is important, but … not enough to explain effects on life cycle/population Energy budgets must be considered direct link to life-history and population effects cover direct and indirect effects

target sitetoxicantphys. process effect on life cycle/population maintenance reproduction … Outlook ? Collaboration with CEH Monks Wood  life-cycle experiments with C. elegans  DEBtox analysis and micro-array work

target sitetoxicantphys. process effect on life cycle/population maintenance reproduction … Outlook ? Why useful?  number of chemicals and species is very large …  but number of target sites and processes is limited!